Machine for making wall board, etc.



Jan. 19, 1926. 1,570,335

H. B. COBB ET AL MACHINE FOR MAKING WALL BOARD, ETC

Filed Nov. 19, 1924 3 Sheets-Sheet 1 v Jan. 19 1926.

H. B. COBB ET AL MACHINE FOR MAKING WALL BOARD, ETC

Fil edNov. 19, 1924 3 Sheets-Sheet 2 v 1,570,335 H. B. COBB ET AL MACHINE FOR MAKING WALL BOARD, ETC

Filed Nov. 19, 1924 5 Sheets-Sheet 3 4 Jan. 19 1926.

Patented Jan. 19, 1926.

UNITED. STATES PATENT OFFICE.

HENRY ."B. COBB AND HARRY W. COBB, :OF MALDEN, MASSACHUSETTS.

MACHINE ron- MAKING- wALL am), ETC.

Application filed Noyem ber 19, 1924. Serial No. 750,884.

To all whom it may camera:

Be it known that we, HENRY 13.001313 and HARRY W. COBB, citizens of the United States, residing at Malden, in the countyof Middlesex and State of Massachusetts, have invented new and useful Improvements in Machines for Making Wall Board, Etc., of which the following is a specification.

This invention relates to machines for making sheets of stiff board such as those used in building construction, as a substitute for lathing and plaster, and composed of freely flowing plastic material containing water, the material being subjected to pressure to express all free water and leave the material solidified in sheet form.

One object of the invention is to provide an automatic machine, adapted to be continuously operated, and to successively produce and deliver sheets of wall board or the like, of a predetermined size.

We attain this and other objects which will hereinafter appear, by the improved construction and combination of parts hereinafter described and claimed.

Of the accompanying drawings forming I a part of this specificatio'n,

Figure 1 is a top plan view of a machine embodying the invention, the charging mechanism shown byv other figures being omitted.

Figure l is a Figure 1. V, 1

Figure 2 is a side elevation of the same.

Figure 2 is a fragmentary view, showing a source of supply of plastic material.

Figure 3 is a fragmentary sectional view, showing a portion of the platen shown by dotted lines in Figure 2.

Figure e1 is a sectional View, showing the two-way valve; shown in elevation by F igure 2.

Figure 4* is a vie-w similar to Figure 1, showing a different adjustment of the valve.

Figure 5 is an end elevation of the mechanism, the conveyor belt being shown section on line l --l of in section on line 55 of Figure 2, parts at the right of said line being omitted.

Figure 6 is a fragmentary vertical section, showing portions of one end of the machine.-

Figure 7 is a fragmentary section, show -the gate.

. Figure 8 is a view similar to Figure 6, showing portions of the opposite end of the machine.

Figure 8 is a view similar to a-portion of Figure 8, showing "a different position-of.

Figure -9 is a fragmentary sectional View, showing a modification.

Figure 10 is a fragmentary side elevation, on a reducedscale, showing the conveyor belt elongated.

The same reference characters indicate the same parts in all of the figures.

The fixed frame or body of the machine forms a chamber in which a platen 12 is the formation of a sheet, thebed l5'support ing the upper stretch of the conveyor belt hereinafter described, and the material, while the latter is being pressed to form a sheet. I

The end walls 14 have transverse openings 17, through which the upper horizontalstretch of an endless porous conveyor belt I 19 passes into and out of the chamber, said stretch being above and in close proximityto the bottom wall 15, as shown by Figures" 6 and 8. i The openings 17 are of'such-size as to permit the passage of a pressed sheet a of wall board therethrough, as indicated by Figure 8, which shows the sheet after it 4 has passed through an opening 17.

The conveyorlbelt may be vmadeof any suitable material or materials, for example,

a layer of woven wire and a layer of felt.

secured by suitable fastenings to the wire layer. Water is therefore enabled to pass golwnward through the top stretch of the The lower portion of the frame below the bed 15, includes side portions 20 and a base 21, forming with the bed, a horizontal passage 22 (Figure 5) through which the lower stretch of the conveyor belt extends.

The corres ending opening 17, at the opposite. end 0 the chamber, is preferably of the same size, said openings being formed to permit the passage therethrough of the composed of oppositely inclined helical pork;

tappets 23,23, fixed to the conveyor belt and prO ecting upward from the u per stretch thereof, as shown by Figure 2, or purposes hereinafter described.

Journaled in bearings outside opposite ends of the frame, are drums 24 and 25 (Figure 2), supporting the conveyor belt 19. The drum 24 is loose, and the drum 25 is fixed to the shaft 27 of an electric motor 28, which is alternately started and stopped by means including one 'of the tappets 23, as hereinafter explained, so that the conveyor belt is driven intermittently by the drum 25, the belt being held stationary while material is being pressed to form a sheet a, and then driven to remove the sheet from the chamber through one ofthe openings 17.

The platen 12 is provided with numerous passages 30, extending through its pressing face for the upward drainage of water expressed from material during the formation of a sheet. Said passages are preferably tapered as shown by Figure 3, so that their walls form seats for ball valves 31, closed by gravity and adapted to be opened by water forced upward through the passages. The object of the valves is to prevent water accumulating in the upper ends of the passages from flowing back through the lower ends. The passages 30 are preferably the tapered bores of tubes 32, inserted 1n soc];- ets in the platen. The upper ends of sand tubes may be provided with woven wire screens 33.

Automatic mechanism is provided for raising and depressing the platen, and holding it at rest for a predetermined period both when fully raised and fully depressed, the preferred mechanism being, as next described.

34 (Figures 1 and 5) designates an electric motor, the shaft 35 of which is adapted to be continuously rotated in one direction, and is connected with the platen by connecting mechanism organized to convert continuous rotation of the motor into reciprocating movements of the platen. Said mechanism as here shewnin'cludes a worm- 36 (Figure 5), fixed to the motor shaft and meshing with a worm gear 37, on a horizontal shaft 38, journaled in' fixed bearings 39 on the to of the machine frame. To the shaft 38 1s fixed a cam, composed of a cylinder 40, and a cam groove formed in the periphery threeof, said groove being tions 41, oblique to the axis of the cam,and dwell portions 42 at right angles with said axis. Said dwell portions are shown by dotted lines in Figure 5, and are at opposite 43 designates a hori-- ends of the cylinder. zontal bar movable longitudinally in fixed guides 44, and provided with a trundle 45 (Figure 5), entering the cam groove and pressed therefrom,

newest with rack teeth 46 (Figure 5), formed on one end portion of the bar, said portion constituting a rack, which meshes with a pinion or gear 47, on a shaft 48 (Figure 1). Said shaft is journaled in bearings 49, on the top of the frame, and is provided at one end with a gear 56, meshing with a gear 57, on a shaft 58, journaled in bearings 59 on the top of the frame. Each of the shafts'48 and 58 is provided with worms 50, meshing with worm gears 52. The hub 53 of each gear 52 is internally threaded,

.as indicated by Figure '1, and constitutes a nut which is rotatable on an externally threaded vertical stem 54, fixed to, and projecting upward from the platen, and movable in fixed guides 55. -Said guides confine the hub 53 and gear 52 against vertical movement, so that their rotation causes a vertical movement of the stem 54 and the platen, there being four stems 54 in this instance, and four worm gears and threaded hubs.

The cam 40 is rotated continuously in one direction by the described connections between it and the motor 34. The arrangement of the portions 41 and 42 of the cam groove is such that when the trundle 45' is in any part of the helical groove portion 41, the bar 43 is moved endwise and causes simultaneous rotation of the worm gears 52 and their nuts, and vertical movement of the platen stems 54.

When the trundle is in either of the dwell portions 42 of the cam groove, the moveits highest position, until the trundle enters the groove portion 41, which is inclined in the opposite direction, whereupon the platen is depressed until the trundle enters the other dwell portion 42. The platen then remains at rest in its lowest position, until the material between it and the upper stretch of the conveyor belt 19, supported by the bed 15, is sufliciently compressed and compacted, and the surplus water; is exthis Water escaping downward through the passages 16 in the bed, and upward through the passages 30, in the platen.

To close the opening 17 in the end walls 14, when the platen is descending and pressing the material, we provide gate 60 (Figures 6 and 8) which are vertically movable in guides 61 (Figure 1) in the side walls 13, and when fully lowered, bear on the conveyor belt, as shown by Figure 6. When the platen is fully depressed, the gates are interposed between the ends of the platen and the end walls 14, the length of the platen '42. The platen then remains at rest in being less than the distance between said walls.

The platen is provided with gate lifters 62, movable in guides 63, and pressed by suflicient force to disenga e the gates from the lifters 62, whereupon t e gates drop upon detents, which are preferably rods 68, movable in guides or brackets 69, on the end walls 14. The detents 68 are normally pressed by springs 70, into the path of the gates, the arrangement being such that the detents support the gates in the partially raised posltion shown by Figure 8, until they are retracted and permit the gates to descend to the 'fully' depressed position shown by Figure 6.

The retraction of the detents 68 is caused by the cooperation of the tappets 23 on the conveyor elt, with bell-crank levers 72, pivoted at 73 to the guides or brackets 69, said levers having slots 74., receiving studs on the detents 68, and trundle rolls 75, normally held by the springs ,in the path of the tappets.

When the conveyor belt is moved in the direction of 'the arrows (Figures 6 and 8),

the tappets simultaneously encounter thetrundle rolls 75 and displace the bell-crank levers, so that the detents 68 are simultaneously retracted. Figure 6 shows a tappet 23 which has just passed a trundle roll 75, and caused the retraction of a detent 68, which is now held retracted by the accompanying gate 60; ready to be projected when the gate again rises.

Figure 8 shows a tappet 23, just before it encounters a trundle roll 75, to cause the retraction of the accompanying detent.

The motor 28 which causes the intermittent movement of the conveyor belt 19, is automatically started and stopped by a circuit closer, which is caused by the projection of the detent 68, shown by Figure 8, to close the motor circuit and start the motor, and is caused by the retraction of said detent to break the circuit and stop the motor. Said circuit closer is shown conventionally by Figures 2 and 8, as including a movable member 78, fixed to and movable with a detent 68, and provided with a contact 79,- and a fixed contact 80, supported by and insulated from one of the guides or brackets 69. Said contacts are connected with circuit wires 81, as best shown by Flgure 2.

'When the detent carrying the contact member 79 is projected, the circuit is closed, as shownby Figure 8, and remainsv closed while the detent is held projected by its spring 70. The circuit is therefore closed and the conveyor belt is driven by the motor while the gates are raised, and until the formed sheet a is removed from the chamber and transferred to another belt 81 (Figure 8), whereby it is carried away to a stacker (not shown).

When the gates are fully depressed, the circuit is broken and the motor and the belt are stopped until the next sheet is formed.

The opening 17 shown by Figure 8, is necessarily formed to permit the removal of the sheet a from the chamber by the belt, and is necessarily closed by a gate to prevent the escape of material through the opening. The only function of the opening 17 shown by Figure 6 is to permit the passage of the tappets 23 into the chamber. Said opening may, therefore, be otherwise formed, and may be closed by means other than a gate 60, so that the machine may be provided with one gate instead of two.

We provide automatic charging means for introducing into the chamber, between the bed 15 and the platen, when the latter is raised, a measured charge of plastic material, sui'ficient for one sheet a. Included in said means are a measuring tank 82, adapted to hold a single charge, and supported in an elevated position above the machine, as shown by Figures 2 and 5, a-

conduit system comprising a supply pipe 87, communicating with a source of supply 87 (Figure 2) of plastic material, pipe connections between the supply pipe 87, the measuring tank and the chamber, a two-way valve, composed of a casing 84, and a movable valve member 86 (Figure 4) controlling said connections to connect the tank with the supply pipe 87 and with thechamber alternately, and valve-operating mechanism operable by 'movements of the platen to connect the supply pipe with the tank and cause the charglng of the latter when the platen is depressed, and to connect the tank with the chamber to cause the transference of the charge from the tank to the chamber when the platen is raised. In this instance, the connection between the delivering end of the supply pipe and the tank isprovided by a pipe 83, oined to the valve casing and the tank. The connection between the tank and the chamber is provided by the pipe 83, the valve casing and a ramified delivering pipe including a main portion 88, joined to the valve casing, branches 89 and 90, joined to the main portion, and terminal portions 91, joined to the branches 90, and to the sides of the tank.

lVhenthe valve member 86 is in the position shown by Figure 4, the supply pipe 87 is connected with the tank 82, and the latter receives a charge. When the valve member is in the position shown by Figure 4 the tank is connected with the chamber and the charge is transferred.

When the tank is being charged, the material flowing through the supply pipe 87 is returned to the source of supply by a return pipe line 92, connected at one end with the valve casing 84, and at the other end with the supply source 87. To permit any surplus material in the tank to return to the source of supply, we provide an overtlow pipe 04, extending from the upper portion of the tank to the return pipe 92. The material may be forced through the supply pipe 87 by a centrifugal pump 87 (Figure 2), which also forces the material through the return pipe 92, when the valve is in the position shown by Figure 4, the

. material flowing through the overflow pipe )4 joining the material in the return pipe, and returning therewith to the source of supply.

The movements of the platen 12 are utilized to move the valve member 86 to the different positions shown, the stem of the valve member being provided with an arm 96 (Figure 2), having a slot 97, receiving a stud 98, on a vertical bar 99, the lower end of which is fixed to the platen 12, as shown by dotted lines in Figure 2. When the platen is raised, the valve member is held in the position shown by Figure 4, and when the platen is depressed, the valve member is held in the position shown by Figure 4.

We provide means for exerting air pressure on the charge in the measuring tank, to force the charge through the ramified delivering pipe line. To this end we connect an air pipe 100, communicating with a source of supply of compressed air, with the upper end of the tank, as shown by Figure 2. The air pipe has an air valve indicated as a whole by 101, the movable member of which has an arm 102 in the path of studs103 and 104, on the vertical bar 99. When the bar rises, the stud 103 moves the arm 102 in the direction required to open the air valve and admit air to the tank. When the bar descends, the stud 104: moves the arm 102 in the opposite direction, and closes the air valve against the admission of air to the tank, and opens the valve for the discharge of air through an exhaust outlet 105.

A cycle of operation of the machine forming and delivering a sheet a is as follows:

en the platen reaches its highest position, the valve member 86 is in the position shown by Figure l, and a charge of material in the measuring tank is transferred to the chamber by gravity and by air 7 pressure through the air pipe 100, the gates v the detents 6S.

and during its descent, air pressure is shut off from the tank after vthe transference of the charge. l/Vhen the platen reaches its lowest position, the gates 60 are engaged by the detent-s 62 (Figure 6). The platen now remains at rest long enough to compact the charge and express the free water' therefrom, through the passages 16 in the bed. and the passages 30 in the platen. When the platen rises, the gates rise with it and the detents 68 are projected by their springs 70 under the gates. When the platen is fully raised, the gate-releasing rods 66 act to disengage the gates from the platen. and permit them to drop upon The conveyor belt 19 has thus far remained at rest. lr' hen the detents are projected, the rod-carrying the movable circuit closing member 79 causes said member to contact with the fixed member 80, and start the motor 28. The conveyor belt now moves sufficiently to convey the sheet a out of the chamber the detents remaining projected until the sheet has been removed.

When the sheet is removed, as shown by Figure 8, the bell-crank levers 72 are simultaneously tripped by the tappets 23, and the detents 68 are retracted to permit the return of the gates to their closed position (Figure 6), and cause one of the detents to break the motor circuit and stop the motor 28. The conveyor belt now stops and the next cycle commences.

The measuring tank 82. is preferably provided with a piston 106 (Figure 2), adapted to be raised by a charge of material, and to be depressed by the air pressure through the air pipe 100.

The upper surface of the platen is preferably inclined downward from its central portion to each of its edges, so that water forced through the'passages 30, flows toward and is discharged from the edges of the platen.

As shown by Figures 5 and 7, the plunger may be provided with knife edged scrapers 107, contacting with side walls 13, to scrape therefrom during the descent of the platen, any plastic material that may adhere to sald Walls. Said scrapers also act to free the edges of the pressed board from the chamber walls, so that the board does not adhere to said walls when the belt is moved to deliver the board. Gutters 108, (Figures 5 and 7), are provided to conduct away water i flowing from the top of the laten through passages 109 in the sides oY the chamber.

The central portion of the base 21 may be depressed, as shown by dotted lines in Figures 2 and 5, and provided with an outlet 110 for water escaping through the bed passages 16.

To remove any plastic material that-may adhere to the lowerstretch of the conveyor belt, we may provide spray pipes 111, and brushes 112, shown by dotted lines in Figure 2, arranged to act on said lower stretch.

To prevent plastic material from lodging in the gate recesses 65, said recesses may be provided with spring-pressed ejectors 113, adapted to yield to the lifters 62, as shown by Figure 9, and to close the mouths of the recesses after the gates are disengaged from the liftei s.

The conveyor belt 19 may be elongated, so that its upper stretch projects sufliciently from the machine to support a formed sheet a outside the chamber, as shown by Figure 10, before the sheet is transferred to the belt 81, and while the next sheet is being formed. A newly formed sheet is, therefore, permitted to harden somewhat while it is supported outside the chamber wholly by the belt 19, so that liability of cracking the sheet during its transference to the belt 81, is prevented' a When the conveyor belt is thus elongated, the means operated by a movement of the belt to stop and start the belt, should be arranged to permit a suflicient carrying movement of the belt to-locate the formed sheet outside the chamber, before the belt is stopped. I

It is obvious that the machine may be used to roduce pressed articles of various forms, rom an suitable plastic material, and that its use 1s not limited to the production of wall board.

We claim: 1. A sheet-forming machine comprising a bed having passages for downward drainage, a platen movable toward and from the bed and having a-ri 'd pressing face and passages for upwar drainage, extending through said face to the upper face of the platen, and a porous conveyor belt, one stretch of which is interposed between the bed and the platen, means being provided for conducting the upward drainage from the u per face of the platen.

2. R sheet-forming machine comprising a bed having passages for downward drainage, a laten movable toward and from the bed an having passages for upward draina e, and a porous conveyor belt, one stretch 0 which is interposed between the bed and the platen, the top surface of the platen being. inclined to conduct the upward drainage to the margin of the platen.

3. A sheet-forming machine comprising a bed having passages for downward drainage, a platen movable toward and from the bed and having passages for upward drainage, and a porous conveyor belt, one stretch of which is interposed between the bed and the platen, the platen passages being tapered and provided with downwardly closing valves.

4. A sheet-forming machine comprising a chamber'including upright side and end walls and a bed forming the bottom of the chamber, and having passages for downward drainage, a platen movable in the chamber toward and from the bed, and having passages for upward drainage, and an inclined top surface, to conduct the upward drainage, to the margin of the platen, a porous conveyor belt, one stretch of which is interposed between the bed and the platen, means for conducting away downward drainage from the bed, and means for conducting away upward drainage from the margin of the platen.

5. A sheet-forming machine comprising a chamber, and a bed forming the bottom of the chamber, a platen movable in the chamber toward and from the bed, a conveyor belt, one stretch of which is interposed between the platen and the bed, one end of the chamber being provided with an opening above the belt, constituting an outlet for a formed sheet, a movable gate adapted to close said opening, and gate- 0 erating means operable by movements of t e platen and belt for alternately opening and closingsaid gate, to prevent the escape of sheet material through said 0 ening during the forming o eration, an to permit the removal of a ormed sheet by the belt after said operation.

6. A sheet-forming machine comprising 'a chamber having transverse openings in the lower portions of opposite walls, and a bed forming the bottom of the chamber; a platen movable in the chamber toward and from the bed, a conveyor belt, one stretch of which is inter osed between the bed and the platen an passes through said openings, movable gates adapted to close said openings, gate openers carried by the platen,

[the openers and gates being adapted to be separably interengaged when the platen 1s depressed, so that the gates are opened when Ill) the platen rises, detents normally projected to sup ort the gates above the openings, gate-re casin means operable by an upward movement of the platen, to disengage the lifters from the gates, and permit the gates to drop upon the detents; and detent-retracting means 0 erable by the belt to permit the closin o the gates.

7. A sheetorming machine as specified by claim 5, comprising also an electric motor for driving the conveyor belt, a circuit closer normally closing the motor circuit to rem der the motor operative, and means operable by a movement of the belt to stop the motor.

8. A sheet-forming machine as specified by claim 6, comprising also an electric motor for driving the conveyor belt, and a circuit closer operable by the projection and retraction of one of said detents to start and stop the motor.

9. A sheet-forming machine as specified by claim 6, comprising also an electric motor for driving the conveyor belt. a circuit closer operable by the projection of one of said detents, to start the motor, and by the retraction of that detent to stop the motor. the machine comprising also detent retracting means operable by the belt.

10. A sheet-forming machine as specified by claim 6, comprising also an electric motor for driving the conveyor belt, a circuit closer operable by the projection of one of said detents, to start the motor, and by the retraction of that detent to stop the motor, the machine comprising also detent retracting means operable by the belt, said detcnt-retracting means including tappets carried by the belt, and bell-crank levers tulcrumed on fined supports and arranged in the path of said tappets.

11. A sheet-forming machine, comprising a chamber having a bottom forming a bed, a platen movable toward and from the bed, a conveyor belt having a stretch interposed between the platen and thebed, a platenoperating motor, connecting mechanism between said motor and the platen, organized to convert continuous rotation of the motor in one direction into reciprocating movements of the platen, a belt-driving motor, and means operable conjointly by movements of the belt and movements of the platen, tor alternately stopping and starting the belt-driving motor, said motor being stopped when the platen is depressed, and started when the platen is raised.

12. A sheet-forming machine as specified by claim 11, said connecting mechanism including a cylindrical grooved cam, rotated in one direction by the platen-operating motor, and having a cam groove including portions of op osite inclination, and dwell portions at rig t angles with the cam axis, a rack-bar engaged with said groove and reciprocable thereby, and connections between said bar and the platen, organized to transmit reciprocating movements to the platen, in a different direction from the movements of the bar.

13. A sheet-forming machine specified by claims 11, said connecting mechanism including a cylindrical grooved cam, rotated in one direction by the platen-operating motor, and havin a cam groove including portions of opposite inclination, and dwell portions at right angles with. the cam axis,

with

net/asst a rack-bar engaged with said groove and reciprocable thereby, screw-threaded stems fixed to the platen, nuts engaged with said stems and confined against movement with the stems, and torque-transmitting connections between the bar and the nuts, organized to rotate the nuts alternately in opposite directions.

14. A sheet-forming machine, comprising a chamber having a bottom formed as a press bed, a platen movable in the chamber toward and lrom the bed, and chambercharging means including a measuring tank above the chamber, a conduit system including a supply pipe communicatin with a source of supply of plastic materia pipe connections between the supply pipe, the measuring tank, and the chamber, a valve controlling said connections to connect the tank with the supply pipe and with the chamber alternately, and valve-operating mechanism operable by movements of the platen. to connect the supply pipe with the tank and cause the charging or the latter when the platen is depressed, and to connect the tanlr with the chamber, to cause the transference of the charge from the tank to the chamber when the platen is raised.

15. A sheet-forming machine, comprising a chamber having a bottom formed as a press bed, a platen movable in the chamber to= ward and from the bed, chamber-charging means including a measuring tank, above the chamber, a conduit system including a supply pipe communicating with a source of supply of plastic material, pipe connections between the supply pipe, the measuring tank and chamber, a valve-controlling said connections, to connect the tank with the supply pipe, and with the chamber alternately, a return ipe communicating with the discharge end of the supply pipe and with the source of supply, a valve controlling said connections and return pipe, and adapted to connect the tank with the supply pipe and with the chamber alternately, and to connect the return pipe with the supply pipe, when the tank is connected the chamber, and valve-operating mechanism, operable by movements of the platen to connect the supply pi o with the tank and cause the charging o? the latter when the platen is depressed, and to connect the tank with the chamber, to cause the transference of the charge from the tank to the chamber, when the platen is raised, the return pipe connecting the delivering end of the supply pipe with the source of supply, when the charge is being transferred,

16. A sheet-forming machine as specified by claim 15, comprising also an overflow pipe, connecting t' e upper portion oil the measuring tank with the return pipe.

17. A sheet-forming machine, comprising a chamber having a bottom formed as a press bed, a platen movable in the chamber toward and from the bed, chamber-charging means including a measuring tank above the chamber, a conduit system including a supply pipe communicating with a source of supply of plastic material, pipe connections between the supply-pipe, the measuring tank,

and the chamber, a valve controlling said connections to connect the tank with the supply pipe and with the chamber alternately, and valve-reciprocating mechanism operable by movements of the platen, to connect the suppl pipe with the tank and cause the charging of the latter when the platen is I depressed, and to connect the tank with the and the tank is charged, and to close said pipe when the platen is depressed and the charge transferred.

18. A sheet-forming machine comprisin a chamber having a bottom forming a be a platen movable in the chamber toward and from the bed,- mechanism for reciprocating the platen, a conveyor belt having an upper stretch interposed between the platen and the bed, intermittently operating belt driving mechanism. the chamber being provided with an opening for the passage of the upper stretch of the belt and a formed sheet carried thereby, and a gate formed to prevent exudation of plastic material through said opening during the formation of a sheet, automatic means being provided for opening the gate to permit the removal of a formed sheet by the belt through said opening.

In testimony whereof we have aflixed our signatures.

- HENRY B. COBB. HARRY W. COBB. 

